* {margin: 0; padding: 0;}
html {
    font-size: 20px;
}
#main {
    position: relative;
}
.box { /*每个图片之间的距离*/
    padding: 0.75rem 0 0 0.75rem;
    float: left;
}
.pic {
    padding: 0.75rem;
    border: 0.05rem solid #ccc;
    box-shadow: 0 0 0.25rem #ccc;
    border-radius: 0.25rem;
}
.pic img { /*所有图片等宽不等高*/
    width: 12.25rem;
    heigth: auto
}